Position sensor with directing mechanism

ABSTRACT

A position sensor for sensing the position of a moving part capable of actuating a plunger belonging to the sensor and more specifically a mechanism for orienting the plunger of the sensor. The sensor includes a guide that is rotationally orientable in a body about a first axis XX′ of rotation, and a plunger sliding without rotation in the guide along the axis XX′. A locator prevents rotation of the guide in the body about the axis of rotation, in a given angular position. The locator is fixed nonremovably in the body and possesses either several tabs spaced regularly about the guide and capable of fitting into one position groove to immobilize the guide or several position grooves in which one tab can fit to immobilize the guide. Such a position sensor may find particular application in detecting the positions of moving mechanical components.

FIELD OF THE INVENTION

The invention relates to a position sensor for sensing the position of amoving part capable of actuating a plunger belonging to the sensor. Morespecifically the invention discloses a mechanism for orienting theplunger of the sensor.

DESCRIPTION OF THE RELATED ART

A position sensor is a device designed to be actuated by a moving part,either because of the shape of its plunger or because of the forcerequired to actuate it.

The position of the moving part is sensed by the mechanical action whichthe part exerts on the plunger when in contact with it.

Position sensors are usually fitted with miniature switches combining areliable system of rapid switching with a sealed enclosure that confinesthe contacts in a neutral gas atmosphere favorable to the switching oflow-level circuits up to high currents. The displacement of the plungerby the moving part actuates the miniature switch and closes or opens anelectrical contact which signals the presence of the moving part.

The shape of that part of the plunger which comes into contact with themoving part is adapted both to the shape of the moving part whoseposition is to be detected and to the type of movement of the part. Thereason for this is that, depending on the configuration of themechanical system in which the sensor is inserted, the angle of attackdefined between the direction of the movement of the moving part and theaxis of the plunger, when contact occurs between the moving part and theplunger, can differ.

For example, if the displacement of the moving part is in the directionof the axis of the plunger, the free end of the plunger can simply be ahemispherical surface giving point contact with the moving part. Withthis same type of displacement, the free end of the plunger may befitted with a ball able to pivot in the plunger in order to providefrictionless contact with the mechanical part, if the latter exhibitslateral movement with respect to the plunger axis.

In cases where the moving part exhibits a linear movement more or lessat right angles to the plunger axis, the plunger comprises at its freeend a roller oriented in the direction of movement of the part, theroller being integral with the plunger and being able to rotate about anaxis of rotation perpendicular to the axis of the plunger.

FIG. 1a shows a partial section through a position sensor 10 accordingto the prior art, comprising a roller 12, a guide 14 that can berotationally oriented about a first axis XX′ of rotation, in a body 16and a plunger 18 sliding without rotation in the guide 14 along thisfirst axis XX′.

At the free end of the plunger is the roller 12 which is of circularcylindrical shape and can turn on a spindle or shaft 20 about a secondaxis YY′ of rotation, this second axis YY′ being colinear with the axisof revolution of the roller, and perpendicular to the first axis XX′.

When a moving part P travelling in a direction Dz approximatelyperpendicular to the first axis XX′ and to the second axis YY′ contactsthe roller 12 on a point of its cylindrical surface situated above thesecond axis YY′, a first force F1 is exerted by the moving part P on theperiphery of the roller. This first force F1, transmitted to the plunger18 through the shaft 20, produces a component force F2 in the directionof the first axis XX′. This component force F2 causes the plunger 18 toslide down the guide 14, and the roller 12 down two guide grooves 22situated in the guide 14 on either side of the first axis XX′.

The sliding of the plunger down the guide takes place without rotation,the second axis YY′ of rotation of the roller 12 being maintained in thesame direction throughout the sliding of the roller in the guide grooves22.

As it slides down the guide 14, displaced by the component force F2towards the interior of the body, the plunger 18 actuates, via a rod 24,an electric microswitch 26. A return spring 28 is compressed during thedisplacement of the plunger towards the interior of the body. When themoving part P moves away from the roller, the plunger 18 is returned toits initial position by the return spring 28.

The body 16 of the position sensor is mounted on a frame (not shown inFIG. 1a) and is thus immobilized in its position with respect to thedirection of displacement of the moving part. As a consequence theroller 12 must be able to be oriented and maintained in its angularposition about the first axis XX′ so that the second axis YY′, aboutwhich the roller revolves, is essentially perpendicular to the directionDz of the movement of the moving part whose position is to be detected.Having the roller oriented in the direction of movement of the movingpart ensures that the roller turns properly on its spindle and avoidslateral loads during contact with the moving part.

To this end, the lower part of the guide 14 comprises position grooves30 distributed around its periphery at an angular pitch a about thefirst axis XX′. At the upper end of the body 16, the sensor possesses alocator 32 which is fixed so that it cannot rotate in the body of thesensor and which is in the form of a washer with a tooth 34 designed tofit into one of the position grooves 30.

The body has a screwthread 35 on its cylindrical outer surface on whicha nut 36 is screwed to clamp the guide 14 and the locator 34 firmly tothe body 16.

FIG. 1b shows a perspective view of the guide 14 showing the positiongrooves 30 distributed around the periphery of the guide at-an angularpitch α of 45 degrees.

An angular position β of the guide grooves 22, and consequently theangular position of the roller 12 sliding in these grooves with respectto a reference axis ZZ′ of the sensor passing through the first axis XX′and through the middle of the tooth 34 of the locator 32, willconsequently be determined by the selection of one of the positiongrooves 30, which contains the tooth 34.

The drawing of FIG. 1c shows a simplified top-down view of the sensortaken on AA′, where the angular position β of the guide grooves 22 isapproximately 90 degrees with respect to the reference axis ZZ′. In thisconfiguration the second axis YY′ of the roller 12 shown in dashes inFIG. 1c will have turned through the angle β of 90 degrees with respectto its position in FIG. 1a.

FIG. 2a shows a view of the principle of a position sensor 40 accordingto the prior art showing another mechanism for the angular positioningof a plunger 42 with respect to a fixed body 44 of the sensor.

The position sensor 40 comprises, as in the case of the sensor of FIG.1a, a guide 46 that can be oriented rotationally about the first axisXX′ in the body 44, with the plunger 42 sliding without rotation in theguide 46 along this first axis XX′.

In this embodiment the guide 46 has first holes 48 distributed radiallywith an angular pitch α about the first axis XX′. The axes of the holesall lie in the same plane perpendicular to the first axis XX′, and eachhole 48 can be lined up with the open end of a second hole 50 in theperiphery of the body 44.

A locator in the form of a flexible circular collar 52 encircles thebody 44 of the sensor around its periphery. FIG. 2b shows the collar 52with a short rod 54 in its center which can be inserted into the secondhole 50 of the body and into one of the first holes 48-1 of the guidelined up with the first. Selecting one of the second holes 48-2 andkeeping it lined up with the first hole by means of the rod 54 ensuresan angularly position β of the guide with respect to the sensor body.

The different mechanisms of angular positioning for sensors in the priorart have drawbacks as follows.

In operation, the sensor suffers impacts when contact occurs between themoving part and the roller. These repeated impacts produce vibrations inthe sensor with the risk of loosening the locator from the sensor body.These vibrations can for example shake the collar 52 free from thesensor shown in FIG. 2a or slacken the nut 36 of the sensor shown inFIG. 1a.

The loosening of the locator and the failure to keep the guide inposition in the sensor body means that the roller is no longer orientedand the position sensing function is therefore no longer performed, withthe consequences which this can engender in systems requiring a highdegree of reliability of operation.

SUMMARY OF THE INVENTION

It is an object of the invention to reduce the problems of the prior artby proposing a position sensor for sensing the position of a moving partcomprising:

a guide that is rotationally orientable in a body about a first axis XX′of rotation, and a plunger sliding without rotation in the guide alongthis axis XX′;

a locator that prevents rotation of the guide in the body about thefirst axis of rotation, in a given angular position, characterized inthat the locator is fixed nonremovably in the body and in that itpossesses either several tabs spaced regularly about the guide andcapable of fitting into one position groove to immobilize the guide orseveral position grooves in which one tab can fit to immobilize theguide.

In one embodiment of the position sensor according to the invention, thetab or tabs are designed to be bent to enable at least one tab to beinserted into a position groove of the guide, in order to preventrotation of the guide in the body.

In a first variant of the sensor according to the invention, the locatorpossesses several tabs, two of these tabs bent, one into each of twoposition grooves of the guide thus preventing the guide from rotating inthe body.

In another variant of the position sensor, the locator possesses onebendable tab and the guide several position grooves, the angularposition of the guide being determined by the choice of one of theposition grooves containing the single bent tab.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will becomeapparent on reading the detailed description given thereof withreference to the attached drawings, in which:

FIGS. 1a, 1 b, already described, show a position sensor and its guide,respectively, according to the prior art;

FIG. 1c, already described, is a simplified top-down view of the sensorshown in FIG. 1a;

FIGS. 2a and 2 b, already described, show another position sensor andits locator, respectively, according to the prior art;

FIGS. 3a and 3 b are a perspective view and a sectional view,respectively, of a position sensor according to the invention;

FIG. 3c is a perspective view of the guide of the sensor shown in FIG.3a, according to the invention;

FIG. 3d is a simplified top-down view of the sensor shown in FIG. 3a,according to the invention.

FIG. 3a is a perspective view of a position sensor 60 according to theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The sensor comprises a guide 62 that is rotationally orientable aboutthe first axis XX′ in a body 64 and a plunger 66 sliding withoutrotation in the guide 62 along the first axis XX′. As in the case of theposition sensors shown in FIGS. 1a and 2 a, the free end of the plungerprojecting from the guide comprises the roller 12, which is able to turnabout the spindle 20 of second axis YY′ perpendicular to the first axisXX′.

FIG. 3b shows a section through the position sensor shown in FIG. 3a, ona plane passing through the first axis XX′ perpendicular to the secondaxis YY′ of the roller 12.

The guide 62, which is of circular cylindrical shape, possesses an upperpart 68 and a lower part 70, the upper part having a smaller diameterthan the lower part which fits inside a first recess 72 in the body 64of the sensor.

The first recess 72, which is of circular cylindrical shape and coaxialwith the first axis XX′, is open in one direction at one end 74 of thebody 64, situated towards the free end of the plunger, and in the otherdirection to a second recess 76, coaxial with the first and of the sameshape, with a diameter slightly smaller than that of the first recess,thus creating a circular shoulder 78 on which a washer 80 sits.

The second recess 76 is open to a third recess 82 through which a lowerpart 84 of the plunger 66 can pass as it slides inside the body 64.

The lower part 70 of the guide is applied, via a base surface 86perpendicular to its axis of revolution, against the washer 80, thuskeeping the guide in its longitudinal position on the first axis XX′ inthe body of the sensor.

A washer-like locator 88 possesses an outer edge 90 and an inner edge92. The locator is crimped by its outer edge 90 into the body of thesensor, near its end 74, coaxially with the first axis XX′.

The locator 88 is crimped into the body 64 of the sensor in such a wayas to clamp the cylindrical lower part 70 of the guide between the saidlocator resting on a circular surface 94 resulting from the intersectionof the upper part 68 with the lower part 70 of the guide, and the washer80. The guide is thus kept in its longitudinal position on the firstaxis XX′, such that it cannot be removed from the body of the sensor,between the locator 88 and the washer 80.

Besides keeping the guide in its longitudinal position in the body ofthe sensor, the locator performs a second function of angularpositioning in the body of the sensor about the first axis XX′.

For this purpose, the locator 88 possesses, on the one hand, notches 96in its outer edge 90, in order to make it rotationally nonremovable oncecrimped into the body 64 and, on the other hand, tabs 98 on its inneredge 92, the tabs being spaced regularly at an angular pitch α about thefirst axis XX′, the faces of the tabs being parallel to the cylindricalsurface of the guide.

The sliding of the plunger 66 in the guide 62 takes place withoutrotation because the second axis YY′ of the roller 12 is maintained inthe same direction throughout the sliding of the plunger as the roller12 slides in the upper part 68 of the guide, in two symmetrical guidegrooves 100 situated on either side of the first axis XX′.

The two guide grooves 100 are continued towards the lower part 70 of theguide 62 as far as the circular surface 94, in the form of two positiongrooves 102 narrower than the guide grooves, and each of which can takeone of the tabs 98 of the locator 88 after bending.

FIG. 3c is a perspective view of the guide 62 comprising the twoposition grooves 102.

Of the tabs 98, FIG. 3b shows two 104 bent almost horizontal either sideof the first axis XX′. The bent tabs 104 fitting into the two respectiveposition grooves 102 in order to prevent the guide 62 rotating in thebody 64 of the sensor.

The choice of which two tabs are bent 104 either side of the first axisXX determines the angular position of the guide with respect to areference direction of the body (which is fixed to a frame) andconsequently the angular position of the roller 12 with respect to thisreference direction.

Specifically, the guide must be oriented in such a way that the twoposition grooves 102 are lined up with the two opposing tabs selectedfor bending. In this embodiment the locator 88 possesses eight tabsspaced at an angular pitch α equal to 45 degrees. The locator cantherefore be oriented in the body with angular increments of 45 degrees.

The angular position β of the guide grooves 100 and consequently that ofthe roller 12 sliding in these grooves, with respect to the body of thesensor, will be determined by which two opposing tabs are selected to bebent into the two position grooves 102.

The drawing of FIG. 3d is a simplified top-down view taken on BB′ of theposition sensor 60, showing the position of the roller 12 with respectto a reference axis VV′ passing through the first axis XX′ and themiddle of a locking groove 106 laid in the body of the sensor parallelto the first axis XX′.

In this illustrative embodiment, the position sensor is fixed withrespect to the direction of movement of the moving part by the way it ismounted on a frame 108. For this purpose, the body of the sensorcomprises on its circular cylindrical surface, a screwthread 110 and thelocking groove 106 parallel to the first axis XX′. A position-definingwasher 112 surrounding the body of the sensor comprises on its inneredge an internal bend 114 which fits into the locking groove 106 and anexternal bend 116 designed to be inserted into a cavity 118 in the frame108. Two nuts 120 and 122 screwed onto the body either side of theposition-defining washer 112 clamp this washer against the frame so thatthe external bend 116 fits into the cavity 118 of the frame 108 andprevents the body of the sensor rotating in the frame.

Two lock washers (not shown in the Figure) can be placed between theclamping nuts 120 and 122 and the frame 108 in order to ensure that thefixing of the sensor to the frame is as reliable as possible.

The embodiment of the locator is not restricted to the example describedand other pitches can be chosen within the limits of the possible waysof constructing the locator and the guide. For example, a pitch of 30degrees results in a locator having 12 regularly spaced tabs.

The locator 88 will be made in a material that will allow the tabs to bebent almost horizontal and unbent to the initial vertical position toallow for the angular position of the roller to be changed a largenumber of times. As an example, the locator may be made of stainlesssteel.

The embodiments of the locator 88 and of the guide 62 are not restrictedto the embodiments described. In other embodiments of the positionsensor, the locator possesses several tabs and the guide a singleposition groove 102, one of the bent tabs fitting into the singleposition groove 102, which means that angular pitches a can be used thatdo not necessarily give rise to two opposing tabs on either side of thefirst axis XX′.

A wiper seal 124 situated at the lower end of the guide in an internalcircular surface 126 of the said guide is held in position in the guideby the washer 80. An O-ring 128 is placed in the second recess 76. Thewiper seal 124 and the O-ring 128 grip the plunger 66, allowing it toslide inside the guide and inside the body of the sensor whilepreventing leaks between the inside of the sensor body and the externalenvironment.

In other applications of the position sensor according to the invention,the moving part has a slot, the position of which must be detected. Forthis purpose the free end of the plunger projecting from the guidecomprises a lever (not shown) integral with the plunger. As with theroller, the lever must be able to be oriented and in this applicationthe lever must be oriented in the direction of the length of the slot ofthe moving part, so that it can fit into the slot of the moving part asit moves. The position sensor according to the invention is excellent inthis type of application.

The position sensor according to the invention has many advantages overthe position sensors of the prior art, namely:

reduced size owing to the disappearance of the systems for locking thelocator, e.g. the locking nuts;

a limited number of parts, reducing the cost of manufacture and thereliability of the product;

ability to be used in numerous applications in civilian and militaryindustry;

great reliability in use compared with sensors of the prior art.

What is claimed is:
 1. A position sensor for sensing a position of amoving part, comprising: a guide that is rotationally orientable in abody about a first axis XX′ of rotation, and a plunger sliding withoutrotation in the guide along the axis XX′; a locator that preventsrotation of the guide in the body about the axis of rotation, in a givenangular position, wherein the locator is fixed nonremovably in the bodyand in that it possesses either several tabs spaced regularly about theguide and configured to fit into one position groove to immobilize theguide or several position grooves in which one tab can fit to immobilizethe guide; wherein the tab or tabs are configured to be bent to enableat least one tab to be inserted into a position groove of the guide toprevent rotation of the guide in the body.
 2. The position sensor forsensing the position of a moving part as claimed in claim 1, wherein thelocator possesses several tabs, two of these tabs bent, one into each oftwo position grooves of the guide.
 3. The position sensor for sensingthe position of a moving part as claimed in claim 1, wherein awasher-like locator possesses an outer edge and an inner edge, thelocator being crimped by its outer edge into the body of the sensor,coaxially with the first axis XX′.
 4. The position sensor for sensingthe position of a moving part as claimed in claim 3, wherein the locatorpossesses notches in its outer edge to make it rotationally nonremovableonce crimped into the body, and tabs on its inner edge, the tabs beingspaced regularly at an angular pitch α about the first axis XX′, facesof the tabs being parallel to the cylindrical surface of the guide. 5.The position sensor for sensing the position of a moving part as claimedin claim 1, wherein the locator possesses eight tabs spaced at anangular pitch α equal to 45 degrees.
 6. The position sensor for sensingthe position of a moving part as claimed in claim 1, wherein the locatorpossesses twelve tabs spaced at an angular pitch α equal to 30 degrees.7. The position sensor for sensing the position of a moving part asclaimed in claim 1, wherein the locator is made of stainless steel. 8.The position sensor for sensing the position of a moving part as claimedin claim 1, wherein a free end of the plunger projecting from the guidecomprises a roller configured to turn about a spindle of a second axisYY′ perpendicular to the first axis XX′.
 9. The position sensor forsensing the position of a moving part as claimed in claim 1, wherein afree end of the plunger projecting from the guide comprises a leverintegral with the plunger.
 10. A position sensor for sensing a positionof a moving part, comprising: a guide that is rotationally orientable ina body about a first axis XX′ of rotation, and a plunger sliding withoutrotation in the guide along the axis XX′; a locator that preventsrotation of the guide in the body about the axis of rotation, in a givenangular position, wherein the locator is fixed nonremovably in the bodyand in that it possesses either several tabs spaced regularly about theguide and configured to fit into one position groove to immobilize theguide or several position grooves in which one tab can fit to immobilizethe guide; wherein the guide, which is of circular cylindrical shape,possesses an upper part and a lower part, the upper part having asmaller diameter than the lower part which fits inside a first recess inthe body of the sensor, the first recess, which is of circularcylindrical shape and coaxial with the first axis XX′ of rotation, beingopen in one direction at one end of the body, situated towards a freeend of the plunger, and in the other direction to a second recess,coaxial with the first recess and of a same shape, with a diameterslightly smaller than that of the first recess, thus creating a circularshoulder on which a washer sits, the second recess being open to a thirdrecess through which a lower part of the plunger can pass as it slidesinside the body, and the lower part of the guide being applied, by abase surface perpendicular to its axis of revolution, against thewasher, keeping the guide in a longitudinal position on the first axisXX′ in the body of the sensor.
 11. The position sensor for sensing theposition of a moving part as claimed in claim 10, wherein the locator iscrimped into the body of the sensor near its end, in such a way as toclamp the cylindrical lower part of the guide between said locatorresting on a circular surface resulting from the intersection of theupper part with the lower part of the guide, and the washer, the guidethus being kept in a longitudinal position on the first axis XX′, suchthat the guide cannot be removed from the body of the sensor, betweenthe locator and the washer.